--TEST--
Bug #80998: Missing second with inverted interval
--FILE--
<?php
$date = new DateTime('2021-04-05 14:00:00');
$interval = new DateInterval('P0DT10799S');
$interval->f = 0.999999;
$interval->invert = 1;
$date->add($interval);
$string = $date->format('Y-m-d H:i:s.u');
echo $string, "\n";
?>
--EXPECT--
2021-04-05 11:00:00.000001